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<title>Property Task</title>
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<body>

<h2><a name="property">Property</a></h2>
<h3>Description</h3>
<p>Sets a <a href="../using.html#properties">property</a>
(by name and value), or set of properties (from file or
resource) in the project.  Properties are case sensitive.</p>
 Properties are immutable: whoever sets a property first freezes it for the
 rest of the build; they are most definitely not variables.
<p>There are seven ways to set properties:</p>
<ul>
  <li>By supplying both the <i>name</i> and one of <i>value</i> or <i>location</i> attribute.</li>
  <li>By supplying the <i>name</i> and nested text.</li>
  <li>By supplying both the <i>name</i> and <i>refid</i> attribute.</li>
  <li>By setting the <i>file</i> attribute with the filename of the property
    file to load. This property file has the format as defined by the file used
    in the class java.util.Properties, with the same rules about how
    non-ISO8859-1 characters must be escaped.</li>
  <li>By setting the <i>url</i> attribute with the url from which to load the
    properties. This url must be directed to a file that has the format as defined
    by the file used in the class java.util.Properties.</li>
  <li>By setting the <i>resource</i> attribute with the resource name of the
    property file to load. A resource is a property file on the current
    classpath, or on the specified classpath.</li>
  <li>By setting the <i>environment</i> attribute with a prefix to use.
    Properties will be defined for every environment variable by
    prefixing the supplied name and a period to the name of the variable.</li>
</ul>
<p>Although combinations of these ways are possible, only one should be used
at a time. Problems might occur with the order in which properties are set, for
instance.</p>
<p>The value part of the properties being set, might contain references to other
properties. These references are resolved at the time these properties are set.
This also holds for properties loaded from a property file.</p>
<p>A list of predefined properties can be found <a
href="../properties.html#built-in-props">here</a>.</p>
<p>Since Apache Ant 1.8.0 it is possible to load properties defined in xml
according to <a href="http://java.sun.com/dtd/properties.dtd">Suns DTD</a>,
if Java5+ is present. For this the name of the file, resource or url has 
to end with <tt>.xml</tt>.</p>

<h3>Parameters</h3>
<table border="1" cellpadding="2" cellspacing="0">
  <tr>
    <td valign="top"><b>Attribute</b></td>
    <td valign="top"><b>Description</b></td>
    <td align="center" valign="top"><b>Required</b></td>
  </tr>
  <tr>
    <td valign="top">name</td>
    <td valign="top">the name of the property to set.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">value</td>
    <td valign="top">the value of the property.</td>
    <td valign="middle" align="center" rowspan="3">One of these or
       nested text, when using the name attribute</td>
  </tr>
  <tr>
    <td valign="top">location</td>
    <td valign="top">Sets the property to the absolute filename of the
      given file. If the value of this attribute is an absolute path, it
      is left unchanged (with / and \ characters converted to the
      current platforms conventions). Otherwise it is taken as a path
      relative to the project's basedir and expanded.</td>
  </tr>
  <tr>
    <td valign="top">refid</td>
    <td valign="top"><a href="../using.html#references">Reference</a> to an object
      defined elsewhere. Only yields reasonable results for references
      to <a href="../using.html#path">PATH like structures</a> or properties.</td>
  </tr>
  <tr>
    <td valign="top">resource</td>
    <td valign="top"> the name of the classpath resource containing
      properties settings in properties file format.</td>
    <td valign="middle" align="center" rowspan="4">One of these, when
      <b>not</b> using the name attribute</td>
  </tr>
  <tr>
    <td valign="top">file</td>
    <td valign="top">the location of the properties file to load.</td>
  </tr>
  <tr>
    <td valign="top">url</td>
    <td valign="top">a url containing properties-format settings.</td>
  </tr>
  <tr>
    <td valign="top">environment</td>
    <td valign="top">the prefix to use when retrieving environment variables. Thus
    if you specify environment=&quot;myenv&quot; you will be able to access OS-specific
    environment variables via property names &quot;myenv.PATH&quot; or
    &quot;myenv.TERM&quot;. Note that if you supply a property name with a final
    &quot;.&quot; it will not be doubled; i.e. environment=&quot;myenv.&quot; will still
    allow access of environment variables through &quot;myenv.PATH&quot; and
    &quot;myenv.TERM&quot;. This functionality is currently only implemented
    on <a href="#notes-env">select platforms</a>. Feel free to send patches to increase the
    number of platforms on which this functionality is supported ;).<br>
    Note also that properties are case-sensitive, even if the
    environment variables on your operating system are not; e.g. Windows 2000's
    system path variable is set to an Ant property named "env.Path"
    rather than "env.PATH".</td>
  </tr>
  <tr>
    <td valign="top">classpath</td>
    <td valign="top">the classpath to use when looking up a resource.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">classpathref</td>
    <td valign="top">the classpath to use when looking up a resource,
      given as <a href="../using.html#references">reference</a> to a <code>&lt;path&gt;</code> defined
      elsewhere..</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">prefix</td>
    <td valign="top">Prefix to apply to properties loaded using <code>file</code>,
    <code>resource</code>, or <code>url</code>.
      A "." is appended to the prefix if not specified.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">prefixValues</td>
    <td valign="top">Whether to apply the prefix when expanding the
      right hand side of properties loaded using <code>file</code>,
      <code>resource</code>, or <code>url</code>.
      <em>Since Ant 1.8.2</em></td>
    <td align="center" valign="top">No (default=<tt>false</tt>)</td>
  </tr>
  <tr>
    <td valign="top">relative</td>
    <td valign="top">If set to <tt>true</tt> the relative path
      to <tt>basedir</tt> is set.  <em>Since Ant 1.8.0</em></td>
    <td align="center" valign="top">No (default=<tt>false</tt>)</td>
  </tr>
  <tr>
    <td valign="top">basedir</td>
    <td valign="top">The basedir to calculate the relative path
      from.  <em>Since Ant 1.8.0</em></td>
    <td align="center" valign="top">No (default=<tt>${basedir}</tt>)</td>
  </tr>
</table>

<h4>OpenVMS Users</h4>
<p>With the <code>environment</code> attribute this task will load all defined
logicals on an OpenVMS system.  Logicals with multiple equivalence names get
mapped to a property whose value is a comma separated list of all equivalence
names.  If a logical is defined in multiple tables, only the most local
definition is available (the table priority order being PROCESS, JOB, GROUP,
SYSTEM).
</p>

<h4>Any OS except OpenVMS</h4>
<p>Starting with Ant 1.8.2 if Ant detects it is running of a Java 1.5
  VM (or better) Ant will use <code>System.getenv</code> rather than
  its own OS dependent native implementation.  For some OSes this
  causes minor differences when compared to older versions of Ant.
  For a full list
  see <a href="https://issues.apache.org/bugzilla/show_bug.cgi?id=49366">Bugzilla
  Issue 49366</a>.  In particular:</p>
<ul>
  <li>On Windows Ant will now return additional "environment
    variables" that correspond to the drive specific current working
    directories when Ant is run from the command line.  The keys of
    these variables starts with an equals sign.</li>
  <li>Some users reported that some Cygwin specific variables (in
    particular PROMPT) was no longer present.</li>
  <li>On OS/2 Ant no longer returns the BEGINLIBPATH variable.</li>
</ul>

<h3>Parameters specified as nested elements</h3>
<h4>classpath</h4>
<p><code>Property</code>'s <i>classpath</i> attribute is a <a
href="../using.html#path">PATH like structure</a> and can also be set via a nested
<i>classpath</i> element.</p>

<h3>Examples</h3>
<pre>  &lt;property name=&quot;foo.dist&quot; value=&quot;dist&quot;/&gt;</pre>
<p>sets the property <code>foo.dist</code> to the value &quot;dist&quot;.</p>

<pre>  &lt;property name=&quot;foo.dist&quot;&gt;dist&lt;/property&gt;</pre>
<p>sets the property <code>foo.dist</code> to the value &quot;dist&quot;.</p>

<pre>  &lt;property file=&quot;foo.properties&quot;/&gt;</pre>
<p>reads a set of properties from a file called &quot;foo.properties&quot;.</p>

<pre>  &lt;property url=&quot;http://www.mysite.com/bla/props/foo.properties&quot;/&gt;</pre>
<p>reads a set of properties from the address &quot;http://www.mysite.com/bla/props/foo.properties&quot;.</p>

<pre>  &lt;property resource=&quot;foo.properties&quot;/&gt;</pre>
<p>reads a set of properties from a resource called &quot;foo.properties&quot;.</p>
<p>Note that you can reference a global properties file for all of your Ant
builds using the following:</p>

<pre>  &lt;property file=&quot;${user.home}/.ant-global.properties&quot;/&gt;</pre>
<p>since the &quot;user.home&quot; property is defined by the Java virtual machine
to be your home directory.  Where the &quot;user.home&quot; property resolves to in
the file system depends on the operating system version and the JVM implementation.
On Unix based systems, this will map to the user's home directory. On modern Windows
variants, this will most likely resolve to the user's directory in the &quot;Documents
and Settings&quot; or &quot;Users&quot; folder. Older windows variants such as Windows 98/ME are less
predictable, as are other operating system/JVM combinations.</p>

<pre>
  &lt;property environment=&quot;env&quot;/&gt;
  &lt;echo message=&quot;Number of Processors = ${env.NUMBER_OF_PROCESSORS}&quot;/&gt;
  &lt;echo message=&quot;ANT_HOME is set to = ${env.ANT_HOME}&quot;/&gt;
</pre>
<p>reads the system environment variables and stores them in properties, prefixed with &quot;env&quot;.
Note that this only works on <em>select</em> operating systems.
Two of the values are shown being echoed.
</p>

<pre>
  &lt;property environment=&quot;env&quot;/&gt;
  &lt;property file=&quot;${user.name}.properties&quot;/&gt;
  &lt;property file=&quot;${env.STAGE}.properties&quot;/&gt;
  &lt;property file=&quot;build.properties&quot;/&gt;
</pre>
<p>This buildfile uses the properties defined in <tt>build.properties</tt>. Regarding to the
environment variable <tt>STAGE</tt> some or all values could be overwritten, e.g. having
<tt>STAGE=test</tt> and a <tt>test.properties</tt> you have special values for that (like another
name for the test server). Finally all these values could be overwritten by personal settings with
a file per user.</p>

<pre>
  &lt;property name=&quot;foo&quot; location=&quot;my/file.txt&quot; relative=&quot;true&quot; basedir=&quot;..&quot;/&gt;
</pre>
<p>Stores the relative path in <tt>foo</tt>: projectbasedir/my/file.txt</p>

<pre>
  &lt;property name=&quot;foo&quot; location=&quot;my/file.txt&quot; relative=&quot;true&quot; basedir=&quot;cvs&quot;/&gt;
</pre>
<p>Stores the relative path in <tt>foo</tt>: ../my/file.txt</p>


<h3>Property Files</h3>

As stated, this task will load in a properties file stored in the file
system, or as a resource on a classpath. Here are some interesting facts
about this feature
<ol>
<li>If the file is not there, nothing is printed except at -verbose log
level. This lets you have optional configuration files for every
project, that team members can customize.
<li>The rules for this format match <a href="http://docs.oracle.com/javase/7/docs/api/java/util/Properties.html#load%28java.io.InputStream%29">java.util.Properties</a>.</li>
<li>Trailing spaces are not stripped. It may have been what you wanted.</li>
<li>Want unusual characters? Escape them \u0456 or \&quot; style.</li>
<li>Ant Properties are expanded in the file</li>
<li>If you want to expand properties defined inside the same file and
  you use the prefix attribute of the task, you must use the same
  prefix when expanding the properties or
  set <code>prefixValues</code> to true.</li>
</ol>
In-file property expansion is very cool. Learn to use it.
<p>
Example:
<pre>
build.compiler=jikes
deploy.server=lucky
deploy.port=8080
deploy.url=http://${deploy.server}:${deploy.port}/
</pre>


<a name="notes-env"></a>
<h3>Notes about environment variables</h3>
<p>
  Ant runs on Java 1.2 therefore it cannot use Java5 features for accessing environment
  variables. So it starts a command in a new process which prints the environment variables,
  analyzes the output and creates the properties. <br>
  There are commands for the following operating systems implemented in
  <a href="https://git-wip-us.apache.org/repos/asf?p=ant.git;a=blob;f=src/main/org/apache/tools/ant/taskdefs/Execute.java;hb=24e5a0e881dba01a6f012c4a271b743946412a0d">
  Execute.java</a> (method <tt>getProcEnvCommand()</tt>):
  <table>
    <tr>
      <th>OS</th>
      <th>command</th>
    </tr>
    <tr>
      <td> os/2 </td>
      <td> cmd /c set </td>
    </tr>
    <tr>
      <td colspan="2"> windows </td>
    </tr>
    <tr>
      <td> * win9x </td>
      <td> command.com /c set </td>
    </tr>
    <tr>
      <td> * other </td>
      <td> cmd /c set </td>
    </tr>
    <tr>
      <td> z/os </td>
      <td> /bin/env <b>OR</b> /usr/bin/env <b>OR</b> env   <i>(depending on read rights)</i> </td>
    </tr>
    <tr>
      <td> unix </td>
      <td> /bin/env <b>OR</b> /usr/bin/env <b>OR</b> env   <i>(depending on read rights)</i> </td>
    </tr>
    <tr>
      <td> netware </td>
      <td> env </td>
    </tr>
    <tr>
      <td> os/400 </td>
      <td> env </td>
    </tr>
    <tr>
      <td> openvms </td>
      <td> show logical </td>
    </tr>
  </table>
</p>

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